Some information on Overview Dates Time And Calendars
, as used in the UUID RFC 4122
is a 60 bit value, representing the number of 100 nanosecond
intervals since 15 October 1582
This guarantees that there would be no duplicates in UUID until 3400 AD. (Then What? ;-) )
is a NumericDate
, it's 00:00:00 of November 17, 1858
(base date of the United States Naval Observatory
Macintosh, it's the midnight beginning January 1 1904
. (MacOS Epoch
System time is measured in seconds or Tick past the epoch.
Sheets uses a form of epoch date
that is commonly used in spreadsheets. The whole number portion of the value (left of the decimal) counts the days since December 30th 1899
. The fractional portion (right of the decimal) counts the time as a fraction of one day
. For example, January 1st 1900 at noon would be 2.5, 2 because it's two days after December 30th, 1899, and .5 because noon is half a day. February 1st 1900 at 3pm would be 33.625.
Note that Google Sheets correctly treats the year 1900 as a common year, not a leap year.
There might be more information for this subject on one of the following: